1. Field of the Invention
This invention relates to a cap for containers having a cylindrical neck, which cap does not require a separate liner to form a liquidtight seal with the rim of the container.
2. Description of the Prior Art
Closures for containers such as bottles or cans having a cylindrical neck have conventionally employed a separate liner made from cardboard, plastic, cork, etc., inside the cap in order to achieve a liquidtight seal between the cap and the mouth or rim of the container neck. Fabrication and insertion of liners into caps require expensive equipment and result in additional costs in assembling the complete cap.
Molded plastic caps have replaced to a substantial extent the metal caps formerly used in sealing containers. In order to overcome the objections inherent in the use of plastic caps with liners, the prior art has proposed a number of constructions for one-piece, plastic caps wherein an integrally formed sealing ring or gasket structure is provided in the upper interior end of the cap. Unfortunately, very few of the proposed, one-piece, linerless caps of the prior art have found acceptance in the marketplace. Many of the proposed linerless caps have complex construction requiring intricate injection molding dies for their production. Additionally, many of the prior art linerless plastic caps have been adapted for use only on bottles having special neck constructions.
Therefore, it can be seen that there is a real need in the marketplace for a simple, economical, readily manufactured, one-piece, linerless plastic cap which obviates the many disadvantages found heretofore in the prior art linerless caps.